Nozzle, particularly for burners

ABSTRACT

A nozzle having a nozzle casing with a whirl member positioned therein and which is pressed against the internally conical bottom of the nozzle casing. The fluid fed to nozzle bore is filtered in a filter and then passes into an annular channel. The latter contains a protective member with passage orifices which are at least as large as the passage orifices of the filter. The protective member holds back any particles detached in the filter or nozzle casing and consequently prevents clogging of whirl channels located in whirl member and of the nozzle bore. It is positioned in immediate proximity of the nozzle bore so as to trap the maximum number of particles.

The invention relates to a nozzle, particulary for burners, whichatomizes a fluid entering said nozzle and which on the inlet side isprovided with a filter in the nozzle casing and on the outlet side has anozzle bore in the bottom of the nozzle casing, a whirl member beingincorporated into the nozzle casing cavity.

Nozzles as defined hereinbefore are widely used in burners for furnacesof all types. The nozzle as well as the nozzle casing are screwed intothe nozzle assembly of the burner. A fluid, e.g. fuel oil is suppliedunder pressure to the nozzle and, generally accompanied by the formationof an angular momentum, is finely atomized by the nozzle bore andsprayed into the combustion chamber where it mixes with the combustionair fed in in the immediate vicinity thereof and ignites.

As the fluid supplied almost always contains impurities, it is known topass the fluid through a filter before it enters the nozzle. Thisfilter, which in the case of small nozzles is generally a sinter filter,is positioned at the inlet side of the nozzle, so that only filteredfluid enters the nozzle and the nozzle bore. The free passasge of thenozzle filter can be made so large that clogging of the nozzle isreliably prevented. This requires a passage width of about 70 to 100μ.

In the case of burners for the heating systems of apartment blocks ithas hitherto been standard practice to design them for a much highercapacity than was necessary for the maximum generation of heat e.g. inwinter. This made it possible to provide the nozzles with sufficientlylarge passage cross-sections, so that there was little risk of clogging.However, as a result of this over-dimensioning of the burners, except inextremely cold weather, it was necessary to frequently switch off theburner to prevent excessive heat production. However, the frequentswitching on and off of the burner is disadvantageous, because the stateat the time of switching on and off does not correspond to thestationary or steady state, which leads to additional losses and alsoburdens the environment with unburned constituents.

With a view to saving oil and providing maximum environmental protectionit is consequently advisable to move away from the conventional burnerdesign and use much smaller burners resulting in far fewer switching onand off states. However, as a result the burner nozzles must bedimensioned for smaller dosing quantitites, which reduces the freepassage cross-section for the fuel oil and therefore increases the riskof clogging. If the size of the passage cross-sections can only bereduced to the extent that the suspended particles in the oil can stillpass through in an unimpeded manner and the variation of the dosingquantity must be achieved through the design of the burner nozzle, it isimpossible to over-look the fact that in spite of the filter there canbe an increase in the number of nozzle blockages. This is due to foreignbodies which can form in the burner nozzles and not to impurities in thefluid, which are retained by the filter. Thus, it is possible thatparticles, e.g. sinter particles can be floated off the filter or metalparticles resulting from the machining or filting operations can bedetached during the operation of the burner nozzle.

The problem of the invention is to so develop a nozzle of theaforementioned type that it is possible to reliably prevent clogging ofthe nozzle by particles which can occur in the latter. According to theinvention this problem is solved in that in the fluid flow path betweenthe filter and the nozzle bore a protective member having passageorifices is provided, the free passage through said passage orificesbeing at least as large as the free passage of the passage orifices ofthe filter.

An embodiment of the invention is shown in the drawing and is describedhereinafter. The drawing is a longitudinal section through a burnernozzle with the object of the invention.

The nozzle shown in the drawing is intended for fuel oil of the typeused in burners. It has a nozzle casing 1 with a bottom 2 containing anozzle bore 3 and having a cylindrical part 4. Nozzle casing 1consequently forms a hollow body, which houses the other parts of thenozzle.

At its free end nozzle casing 1 has an internal thread 5 and an externalthread 6, the latter being used for screwing the nozzle into the notshown burner nozzle assembly.

Within nozzle casing 1 is mounted a whirl member 7 having a whirl memberhead 8 with whirl channels 9 and a whirl member shaft 10. Head 8 isconical and rests on the inside of a cone-forming bottom 2. The conicalsurface of whirl member head 8 and the cone of bottom 2 form a completeseal, so that the fluid flowing through the nozzle can only flow inthrough the whirl channels 9 of nozzle bore 3.

An assembly sleeve 11 with radial bores 12 is placed on whirl membershaft 10. Whirl member 7 is pressed via assembly sleeve 11 onto the coneof bottom 2 by an assembly screw 13 screwed with an external thread 14into the internal thread 5 of nozzle casing 1. An axial bore 15 isprovided in assembly screw 13. A pin 16 positioned on assembly screw 13permits the screwing in of the latter, e.g. by constructing pin 16 withcross-slots or some other displacement possibility.

The internal thread 5 of nozzle casing 1 is also used for screwing on afilter 17. Filter 17 is mounted in a filter base 18 with a flange 19 andan external thread 20, which is screwed into the internal thread 5 ofnozzle casing 1.

A protective member 21 is positioned between the shoulder formed bywhirl member head 8 and assembly sleeve 11. Member 21 is in the form ofa circular disk of sieve or screen material and is pressed against theshoulder of whirl member head 8 by sleeve 11. The function of protectivemember 21 is not to additionally filter the inflowing fluid. Thereforethe passage orifices should be at least as large as the passage orificesof filter 17 and can be even larger than the filter orifices. However,they are still able to retain any particles floated off the filter orwhich become detached during assembly, e.g. on screwing together theparts or in operation. It is important that protective member 21 ispositioned as close as possible to the nozzle bore, so that particlescannot appear between protective member 21 and nozzle bore 3. As isapparent from the drawing this is achieved through constructingprotective member 21 and a sieve material ring. The fluid cleaned in thefilter 17 admittedly passes through the ring, but is subject to nofurther filtering action due to same size of passage orifices 22. Thefunction of protective member 21 is not to again filter the alreadyfiltered fluid, but to retain particles formed in filter 17 or nozzlecasing 1.

Surprisingly protective member 21 makes it possible to operate in asubstantially trouble free manner nozzles with a small passagecross-section. The fluid flowing through filter 17 passes via the axialbore 15 of assembly screw 13 into an area 23 surrounded by assemblysleeve 11 and from there via radial bores 12 into an annular channel 24in which protective member 21 is positioned in the immediate vicinity ofnozzle bore 3. Protective member 21 holds back any particles appearingin the filter and the fluid flow path, thereby substantially ensuringthat there is no clogging of whirl channels 9 or nozzle bore 3.

I claim:
 1. A nozzle for atomizing a fluid especially for use inburners, comprising: a hollow nozzle casing having an inflow side and anexit bore, a filter located at said inflow side and having orifices witha free passage, a whirl member in said casing and having a whirl memberhead at said exit bore, an annular channel between the inner wall ofsaid casing and said whirl member, and an annular protective memberformed by a sheet of sieve material in said annular channel at saidwhirl member head and having orifices with a free passage larger thanthe free passage of said filter orifices, said sheet being positionedbetween said whirl member head and an assembly sleeve, said annularchannel being defined by the inner wall of said nozzle casing and theouter wall of the assembly sleeve, whereby impurities contained in thefluid are retained in the filter, and impurities originating from thenozzle are retained by said protective member.